Demystifying useEffect: React’s Swiss Army Knife for Side Effects

A simplified guide to mastering React’s do-it-all hook for effects and cleanup

Photo by Paul Felberbauer on Unsplash

Among React’s wide array of hooks, useEffect stands out for handling the diverse range of side effects and async behavior needed in components.

However, understanding exactly when and how to apply useEffect can be one of React’s trickier concepts for newer developers. In this guide, let’s unravel the mystery behind this Swiss army knife of effects!

Declarative Re-Renders, Meet Side Effects

At its core, React focuses on declarative rendering of components driven by state:

function MyComponent() {
  const [count, setCount] = useState(0);  
  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );

}

This fully captures React’s intended re-rendering paradigm. However, many components also need to produce side effects like:

• Data fetching
• Interacting with DOM APIs
• Manual event listeners
• Server-side integration